Synergistic visbreaking composition of peroxide and hydroxylamine ester for increasing the visbreaking efficiency

Abstract

Synergistic visbreaking composition of peroxide and a hydroxylamine ester for increasing the visbreaking efficiency for polypropylene polymers at melt extrusion temperatures below 250° C. and its use in visbreaking polypropylene. The present invention is furthermore related to the use of such visbroken polypropylene polymers for producing melt blown non-wovens with improved barrier properties.

Claims

1. A synergistic visbreaking composition of peroxide and a hydroxylamine ester for increasing the visbreaking efficiency for polypropylene polymers at melt extrusion temperatures below 250° C., comprising peroxide (i) and hydroxylamine ester (ii) in a range of from 1 wt % (i):99 wt % (ii) to 99 wt % (i): 1 wt % (ii) wherein the hydroxylamine ester is selected from the group consisting of sterically hindered amine derivatives of the formula: ##STR00009## and the peroxide is selected from the group consisting of 2,5-dimethyl-2,5-bis(tert.butyl-peroxy)hexane, 2,5-dimethyl-2,5-bis(tert.butyl-peroxy)hexyne-3, dicumyl-peroxide, di-tert.butyl-peroxide, tert.butyl-cumyl-peroxide and bis (tert.butylperoxy-isopropyl)benzene.

2. (canceled)

3. The synergistic visbreaking composition according to claim 1, comprising pure peroxide (i) and pure hydroxylamine ester (ii) in a range of from 20 wt % (i):80 wt % (ii) to 95 wt % (i):5 wt % (ii).

4. The synergistic visbreaking composition according to claim 1, wherein a to be visbroken polypropylene is a propylene homopolymer or a propylene copolymer with up to 10 wt % of comonomer selected from ethylene, 1-butene, 1-hexene and 1-octene.

5. A method comprising: increasing the melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 of polypropylene polymers at melt extrusion temperatures below 250° C. by adding the synergistic visbreaking composition of peroxide (i) and a hydroxylamine ester(ii) according to claim 1 to a polypropylene polymer to be visbroken.

6. A method for increasing the visbreaking efficiency for polypropylene polymers at melt extrusion temperatures below 250° C. comprising: adding the synergistic visbreaking composition of peroxide (i) and a hydroxylamine ester(ii) according to claim 1 to a polypropylene polymer to be visbroken.

7. A method comprising: forming melt blown non-wovens with improved barrier properties from polypropylene polymers being visbroken with a synergistic visbreaking composition comprising peroxide (i) and hydroxylamine ester (ii) in a range of from 1 wt % (i):99 wt % (ii) to 99 wt % (i):1 wt % (ii).

8. A melt blown non-woven comprising polypropylene polymers being visbroken with the synergistic visbreaking composition according to claim 1.

9. An article selected from the group consisting of filtration media (filter), diapers, sanitary napkins, panty liners, incontinence products for adults, protective clothing, surgical drapes, surgical gown, and surgical wear in general, comprising the melt-blown non-wovens according to claim 8.

10. The synergistic visbreaking composition according to claim 3, comprising pure peroxide (i) and pure hydroxylamine ester (ii) in a range of 25 wt % (i):75 wt % (ii) to 90 wt % (i):10 wt % (ii).

11. The synergistic visbreaking composition according to claim 3, comprising pure peroxide (i) and pure hydroxylamine ester (ii) in a range of 30 wt % (i):70 wt % (ii) to 85 wt % (i):15 wt % (ii).

12. The synergistic visbreaking composition according to claim 3, comprising pure peroxide (i) and pure hydroxylamine ester (ii) in a range of 50 wt % (i):50 wt % (ii) to 85 wt % (i):15 wt % (ii).

13. The synergistic visbreaking composition according to claim 4, wherein the to be visbroken polypropylene is a propylene homopolymer.

14. The method according to claim 6, comprising adding the peroxide (i) and hydroxylamine ester(ii) as a mixture to the polypropylene polymer to be visbroken.

15. The method according to claim 6, comprising adding the peroxide (i) and hydroxylamine ester(ii) as individual components to the polypropylene polymer to be visbroken.

Description

EXPERIMENTAL PART

A. Measuring Methods

[0097] The following definitions of terms and determination methods apply for the above general description of the invention including the claims as well as to the below examples unless otherwise defined.

[0098] Calculation of Total Expected MFR.sub.2

[0099] Under the proviso that the total MFR of the composition visbroken with peroxide and hydroxylamine follows the additive law, the total MFR will be the sum of the MFR(peroxide)+MFR (hydroxylamine).

[0100] Meaning that the calculated MFR is the sum of MFR of material visbroken only with peroxide and the MFR of material visbroken only with hydroxylamine ester, which have been measured (see also FIG. 1)

[0101] MFR.sub.2 (230° C.) is measured according to ISO 1133 (230° C., 2.16 kg load). The MFR.sub.2 of the polypropylene composition is determined on the granules of the material, while the MFR.sub.2 of the melt-blown web is determined on cut pieces of a compression-molded plaque prepared from the web in a heated press at a temperature of not more than 200° C., said pieces having a dimension which is comparable to the granule dimension.

[0102] Hydrohead

[0103] The hydrohead or water resistance as determined by a hydrostatic pressure test is determined according to the WSP (worldwide strategic partners) standard test WSP 80.6 (09) as published in December 2009. This industry standard is in turn based on ISO 811:1981 and uses specimens of 100 cm.sup.2 at 23° C. with purified water as test liquid and a rate of increase of the water pressure of 10 cm/min. An H.sub.2O column height of X cm in this test corresponds to a pressure difference of X mbar.

[0104] Filtration Efficiency

[0105] Air filtration efficiency was determined based on EN 1822-3 for flat sheet filter media, using a test filter area of 400 cm.sup.2. The particle retention was tested with a usual aerosol of di-ethyl-hexyl-sebacate (DEHS), calculating efficiency for the fraction with 0.4 μm diameter from a class analysis with 0.1 μm scale. An airflow of 16 m.sup.3.Math.h.sup.− was used, corresponding to an airspeed of 0.11 m.Math.s.sup.−.

B. Examples

[0106] Materials Used

[0107] PP-Homo-1: HC001A-B1: propylene homopolymer with a density of 905 kg/m .sup.3 and an MFR (2.16 kg, 230° C.) of ˜3.7 g/10 min. It is distributed by Borealis.

[0108] PP-Homo-2: HJ120UB: propylene homopolymer of Borealis with an MFR.sub.2 (2.16 kg, 230° C.) of 75 g/10 min, and a density of 0.905 g/cm

[0109] PP-Homo-3: HD120MO: propylene homopolymer of Borealis with an MFR.sub.2 (2.16 kg, 230° C.) of 9 g/10 min and a density of 0.905 g/cm

[0110] Antioxidant (AO): Irganox 1010 (FF) provided by BASF

[0111] Acid Scavenger (AS): Calcium stearate provided by Faci.

[0112] Pure PDX: peroxide pure: 2,5-dimethyl-2,5-bis(tert.butyl-peroxy)hexane (DHBP) (CAS No. 78-63-7; sold under trade nameTrigonox 101 from AkzoNobel, NL)

[0113] Peroxide (PDX PP5% ig): Masterbatch 5% in PP: DHBP-5-ICS produced by United Initiators.

[0114] (5% 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane (DHBP) in 95% PP)

[0115] Hydroxylamine ester: Irgatec® CR 76, Masterbatch 3.3 wt % in PP, provided by BASF (Irgatec® MB)

[0116] Thio-Compound 1: 1-Octadecanethiol, CAS NO. 2885-00-9, assay 98% was purchased from Sigma Aldrich and used as it is.

Example IE1 to 1E3+CE1 to CE5

[0117] X wt % PP-Homo-1 were mixed with 0.1 wt % Irganox 1010 (FF), 0.05 wt % Calcium stearate (CAS No. 1592-23-0) y wt % Peroxide Masterbatch and z wt % Irgatec ® CR 76 Masterbatch by using extruder ZSK 18 at 240° C., with a throughput of 7 kg/h.

[0118] The wt % amounts can be seen in Table 1. Furthermore the MFR.sub.2 (2.16 kg, 230° C.) values are given in Table 1.

TABLE-US-00001 TABLE 1 Example CE1 CE2 CE3 IE1 IE2 IE3 CE4 CE5 Component [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] PP-homo-1 99.85 98.25 99.05 98.25 98.25 98.25 99.05 98.25 AO 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 AS 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 POX PP5% ig 0 1.6 0.8 0.4 0.8 1.2 0 0 Irgatec ® MB 0 0 0 1.2 0.8 0.4 0.8 1.6 MFR.sub.2 3.76 35.3 16.17 34.16 36.19 37.14 9.1 18.4 IE . . . Inventive Example CE . . . Comparative Example

[0119] Table 2 shows the calculated MFR.sub.2 (2.16 kg, 230° C.) that has been expected compared to the real MFR.sub.2 (2.16 kg, 230° C.)

TABLE-US-00002 TABLE 2 Irgatec ® POX MB MFR PP5% ig MFR Additive MFR 1.6 [wt %]- [wt %] Calc. [wt %] Calc. raw real POX [wt %] 0.4 6.7 1.2 26.3 33.0 37.14 0.4 0.8 10.4 0.8 18.4 28.8 36.16 0.8 1.2 14.1 0.4 10.5 24.6 34.16 1.2 1.6 18.4 1.6 35.3 0

[0120] FIG. 1 shows the MFR.sub.2 values for the addition of only PDX PP5% ig or only Irgatec® MB

[0121] FIG. 2 shows the calculated MFR.sub.2 values vs. the real MFR.sub.2 values for 1.6 wt % of total visbreaking agent minus the wt % of PDX (peroxide) used.

Example 1E4 and CE6 and CE 7

[0122] PP-homo-2 was mixed with 0.1wt % Irganox 1010 (FF) and 0.05 wt % Calcium stearate (CAS No. 1592-23-0).

[0123] Then PP-homo-2 has been visbroken by using a co-rotating twin-screw extruder at 240° C. and using 1700 ppm pure PDX (Trigonox 101) to achieve the target MFR.sub.2 of 800 g/10 min for CE6.

[0124] For CE7 1.5 wt % of Irgatec® CR76 MB was used to achieve the target MFR.sub.2 of 800 g/10 min.

[0125] For IE4 1.1 wt % of Irgatec® CR76 MB and 300 ppm pure PDX (Trigonox 101) was used to achieve the target MFR.sub.2 of 800 g/10 min. The polypropylene compositions of IE4, CE6 and CE7 have been converted into melt-blown non-woven webs on a Reicofil MB250 line using a spinneret having 470 holes of 0.4 mm exit diameter and 35 holes per inch. Webs were produced at different melt temperatures, throughputs, DCD (die to collector distance) and air volumes.

[0126] The processing conditions for and properties of the melt-blown webs are indicated in tables 3 and 4

TABLE-US-00003 TABLE 3 Processing conditions for the production of the melt-blown webs Melt Air Web Temperature DCD volume Throughput weight MFR web Example ° C. mm m.sup.3/h kg/h .Math. m g/m.sup.2 g/10 min IE4 270 200 270 10 9.5 1041 CE6 270 200 310 10 10 1000 CE7 270 200 200 10 9.5 976

TABLE-US-00004 TABLE 4 Properties of the melt-blown webs Filtration Quality Hydrohead Efficiency factor (3.sup.rd drop) Example % 100/Pa cm H.sub.2O* IE4 36.7 0.597 106.6 CE6 25.18 0.561 81.5 CE7 30.52 0.627 88.4

[0127] As can be seen from Table 4 and from FIG. 3 the use of polypropylene polymer, which has been visbroken with the inventive synergistic visbreaking agent composition for producing melt blown non-woven webs gives webs having higher hydrohead values compared to the comparative examples.

Comparative Example 8

[0128] For this Comparative Example PP-homo-3 has been visbroken by Irgatec® MB and/or by Thio-1 by using extruder ZSK 18 at 250° C., with a throughput of 7 kg/h.—results see Table 5

TABLE-US-00005 TABLE 5 Irgatec ® Irgatec ® MB + No MB Thio-1 Thio-1 visbreaking [wt %] [wt %] [wt %] PP-homo-3 100 wt % 99.725 99.775 99.698 Irgatec ® MB  0 0.08 0 0.08 Thio-1  0 0 0.025 0.025 MFR.sub.2  8 10.5 15.3 14.1

[0129] As can be seen from FIG. 4 there is absolutely no synergistic effect by using Irgatec® in combination with Thio-1 in view of visbreaking efficiency.